Overload relay



Oct' 11 1927'a jgy:

llllllllll llllll J. H' PENGILLY OVERLOAD RELAY Filed Dec. 29. 1926 2 Sheets-Sheet 1 Oct. 11, J. H. PENGILLY OVERLOAD RELAY Filed Dec. 29, 1926 2 Sheets-Sheet fr? TTOfj/EX Patented Oct. 11, 1927.

UNITED STATESy PATENT OFFICE.

JOSEPH H. PENGILLY, OF LOS ANGELES, CALIFORNIA, ASSIGNOR T0 BROWN ,& PEN- GILLY, INC., 0F LOS ANGELES, CALIFORNIA, A CORPORATION 0F CALIFORNIA.

ovERLoAD RELAY.

Application led December 29, 1926. Serial No. 157,797.y

My invention relates t-o overload relays which break an electric circuit when the current flowing through the circuit increases above a predetermined amount.

The overload relay lof my invention is particularly adapted for breaking the circuit of an induction motor when the motor draws too heavy a current, so that the primary windings will not be burned out. My in-v vention may however be used successfully in other installations;

It is an object of this invention toprovide an overload relay which is thermostatically operated.

Another object of this invention is to provide an overload relay which is adjustable and may be set to operate at different flows of current through the circuit which it is adapted to control.

Other objects and advantages of the invention will be made evident hereinafter.

Referring to the drawings in which my invention is illustrated,

Fig. 1 is an elevational view of the invention.

, Fig. 2 is a sectional view taken as indicated by the line 2--2 of Fig. 1.

Fig. 3 is a section taken on the line 3--3 of Fig. 1.

Fig. 4 is a section taken on the line 4-4 of Fig. 1.

Fig. 5 is a fragmentary perspective view showing the means for adjusting the thermostatic element of the invention. l

Fig. 6 is a fragmentary section taken on the line 6-6 of Fig. 5.

Fig. 7 is a diagrammatic view illustrating the manner in which the invention is connected in the circuit of an induction motor.

The invention provides a housin consisting of a base plate 11 formed of insulation material, and a metallic casing 12 which is secured to the base plate 11 by screws 13. Supported Pinside the housing is an insulation mounting block 14. is supported by attachment bolts 16 inside the housing and a distance from the plate 11. Attached to the mounting block 14 at opposite ends thereof are outer brackets 18. The outer brackets 18 have legs 19 which engage the back face of the mounting block 14 and The mounting 14l through which screws 20 are extended for securing the outer brackets to the mounting block. Extended from the legs 19 at right angles to the plane of the mounting block 14 are legs 21. The legs 21, as illustrated best in Figs. 1 and 5, are arranged at the right side of the block 14. Inner brackets 23 are supported by the mounting block 14. The inner brackets 23 have legs 24 which engage the back face of the mounting block 14 and through which screws 25 are extended for attaching the inner brackets to the mounting block. Extended from the legs 24 at right angles theretoand at right angles to the plane of the mounting block 14 arer legs 26. The le s 26. are projected through openings 27 formed in the mounting block 14. The legs 26 are in such positions that the left edges thereof are substantially aligned with the left faces of the legs 21.

The inner and outer brackets 18 and 23 are arranged in pairs, as shown, and connected to each of the brackets of the pairs is a heating element 28. The heating 4elements 28 are secured to thelegs 21 and 26 of the brackets 18 and 23 by suitable bolts 29. These elements 28 are made from a resistance material which will heat readily when an excessive current flows therethrough. The heating elements may be made from any suitable material such as German silver.

vAttached to the front face of the mounting block 14 adjacent to the heating elements 28 are fla-tmetallic plates 33 which are secured to the mounting plates 14 by bolts 34 and 35. The bolts 35 areplaced at the inner ends of the plates 33 and on these bolts 35 adjustment members -36 are pivoted. The adjustment members 36 have body portions 37 which lie against the plates 33 and have arms 39 extending from the body portions 37 at the outer ends thereof and at right angles to the plane of the mounting block 14. The arms 39 extend upward adjacent to the heating elements 28. Connected to the upper ends of the arms 39 by rivets 40 are bimetallicthermostatic elements 41. The bimetallic thermostatic elements 41 extend substantially paral-l lel to the heating elements 28. The positions of the adjustment members 36, and

consequently the positions of the bimetallic elements 41, may be regulated by a means which will now be described.

The legs 39 have short portions 44 which are provided with vertical slots 45. Threaded shafts 46 are provided with channels or grooves 47 so that the ends thereof may be Screwed onto'the ends of the shafts 46l in back of the legs 49 are adjustment members in the form of nuts 50. Nuts 50 are provided with arms 51 by means of which they may be conveniently rotated, and are provided with graduations 52 which may be selectively aligned with marks 53 provided at the upper part of the legs 49 to facilitate the accurate setting of the thermostatic elements 41. Springs 54 are,compressed between the portions 44fof the legs 39 and the legs 49 of the plates 33. The springs 54 hold4 the adjustmentimembers 36 as far to the right as the nuts 50 will permit.

Extended upward from the mounting` block 14 between the inner brackets 23 is a post 56. Attached to the post 56 and eX- tending leftward are arms 57 which pivotally support an engager 58. The engager 58, as shown best in Fig. 4, is pivoted to the arms 57 by means of a pin 59. The upper end. of the engager 58 is provided with a pair of opposing shoulders 60 which may be .engaged by the inner ends of the thermostaticelements 41. Extending to the right between the shoulders 60 is a stop extension 62 which determines one positionof the engager. The engager is resiliently retained in this position by means of a compression spring 63.

Attached to the left part of the mounting block 14 are finger contacts 64 and 65 of a throw-out switch of the invention. These finger contacts 64 and 65 are secured to the mounting block b y suitable bolts 66. The left ends of the linger contacts 64 and 65 are spaced a distance from each other but the right ends thereof rest in such-positions that the right end of the finger contact 64 rests belowl the right end of the finger con-W tact 65. The finger contacts 64 and 65 are provided at the right ends with contact bosses 68. The finger contact 64 is provided with a restraining plate 69 which ,is attached in place by one of the bolts 66 for preventing this contact from moving upward beyond acertain position.

The engager 58 is provided with a. lower engaging end 70 which is adapted to engage the right end of the finger contact and hold it in a down position, as illustrated in Fig. 4, so that contact will be made between the contact bosses 68 of it and the finger contact 64. The engager 58, however,

cannot move into engaging position until the finger contact 65 has been moved downward so that the engaging end 70 may move in a. leftward direction above the end of this contact.

For the purpose of depressing the finger contact 65, I provide a re-set member 73 which is pivoted on a pin 74, which pin 74 is supportedy by a bracket 75. Thev bracket 75 is mounted on the mounting block 14. The re-set member 73 is made from insulation material and is triangular in shape. The lower end is provided with an engagement boss 76 which is adapted to engage the finger contact 65 and depress it. For the purpose of moving the re-set member 73 I provide a pull rod 77 which is attached to the re-set member 73 at 78 and which extends l.downward through an opening 8O in the lower part of the shell 12. The lower end of the pull rod 77 is provided with a handle 81 by means of which it may be engaged and pulled downward. A spring 82 is compressed between the shell 12 and a washer 83 secured to the pull rod 77, for the y purpose of returning the pull rod 77 and the re-set member 73 to original position, so that the re-setmember 73 will not engage the finger contact 65 and prevent it from being moved quickly into released position when it is released by the engager 58.

The overload relay `of the invention is attached to an electric circuit, as shown in Fig. 7. In Fig. 7 the numeral 86 represents an induction motor having a rotor 87 and a three-phase primary winding 88. Extending from the primary winding 88 are conductors 90, 91 and 92 of a three-phase electric circuit. The conductors and 91 have a heating element 28 of the invention included in each.l The conductors 90 and 91 havewires 94 which are connected to the left ends of the outer brackets 18 by means of bolts 95, as shown in Fig. 2, and they have wires 96 which are connected to the inner brackets 23 by bolts 97. The finger contacts 64 and 65 are connected to the conductors 99 and 100 by means of the bolts 66. The conductor 99 includes a battery or other source of electrical energy, as indicated at 101, and theconductors 99 and 100 both extend to a solenoid 103 which is adapted to maintain a main switch 104 closed against the action of a spring 105 when the finger contacts 64 and 65 are in engagement with each*j other. When the main switch 104 is open the supply of current to the induction motor 86 1s discontinued.

The operation of the invention is substantially as follows.

In the first place the flow of current to any phase of the primary Winding 88 'must flow through one of the heating elements 28. This is accomplished by providing a heating element in two of the conductors of the lill y three-phase circuit. During the usual operation of the motor 86 the proper ioxv of current will pass through the conductors 90 and 91 and the heating elements 28 will be warmed but will not be overheated. In event that the motor should be overloaded and in event that the motor should draw the excessive flow of current through either ot' the heating elements 28, the heavy flow will cause it to heat up. The excessive heat produced by either or both of the hea-ting elements 28 will cause the thermostatic element 41 adjacent thereto tobend. The inner end of the heated thermostatic element 41 will bend in a leitward direction and bear against an adjacent shoulder 60 of the engager 58.J

It the excessive current is only temporary, the heating elements 28 will not be heated enough to bend the thermostatic elements 41 suficiently to operate the engager 58, but if' this abnormal condition exists for a short period the inner ends of the thermostatic elcments, either one or both of them, will move into possitions indicated by dotted lines 107 in Fig. 4 and will therefore move the engager 58 against the action of the spring 63 into a position indicated by dotted lines 108 of Fig. 4. When the engager 58 is moved into this position, the inner end of the finger contact 65 is released and may be moved up into a position indicated by dotted lines 109 of Fig. 4. It will be seen that this breakscontact between the finger contacts 64 and 65 and deenergizes the solenoid 103. The main switch 104 is then opened by the action ot the spring 105 and this will arrest the supply of current to the induction motor 86.

In order to again supply current to the motor 86 it is necessary to close the main switch 104 and this is accomplishedby closing the throw-out switch of my invention. This throw-out switch, as previously ex plained, is the finger contacts 64 and v65.

The closing of this switch is done by pulling' down on the handle 81 which is4 attached to the pull rod 77. This willl swing the lower end of the re-set member 73 in a right direction in Fig. 3 so that the engaging portion 76 will engage the contact finger 65 and return it to the position shown in full lines in Fig. 4. This will close the throw-out switch and the solenoid 103 will be energized so that the main switch 104 of the circult to the motor 86 is closed. At this time if the thermostatic elements have returned to normal position, the engager 58 will move under the action of the spring 63 from the position indicated by dotted lines 108 in Fig. 4 into full line possition shown in that figure, and will engage the inner end of the nger contact and hold the contact bosses 68 in engagement. The motor 86 will then be 'supplied with current until the circuit to the solenoid 103 is intentionally broken by ope` erating a switch 116, or is broken by an excessive fiow of current which causes the contacts 64 and 65 to be separated as previously explained.

In my invention Ait is possible to adjust the positions ofthe thermostatic. elements 41 so Anv adjustment of the nuts 50 causes the shafts 46 to move axially in either direction and causes the adjustment members 36 to swing in either direction on their pivots 35. When the adjustment members 36 are moved, the thermostatic elements 41 are also, moved so that the inner ends thereof either move toward or away from the shoulders 60 provided by the engager 58. If the inner ends of thethermostatic elements 41 are moved towards these shoulders 60, theheat necessary to disengage the engager 58V will be decreased; and if the inner ends of the thermostatic elements 41 are moved away from the shoulders 60, the heat necessary to operate the engager 58 will be increased. It' should be understood that theheat provided by the heating elements 28 is in proportion to the flow of' current therethrough; therefore, by requiring more heat to cause the thermostatic elements 41 to act-nate the engager 58, the circuit of the motor 86 will not be broken until a current necessary to heat the elements 28 to this degree is drawn by the motor.

It is highly desirable in providing apparatus for the protection of electrical machinery that the characteristics of the protective apparatus' be such as to protect the electrical apparatus at all timesand under all conditions.

It is also highly desirable that the apparatus be so constructed that the circuit is never opened unless there is actual need for it. For many years it was the practice to provide overload circuit breakers which were operated by a coil or magnet energized from the main4 circuit to be protected.y It

was found that these circuit breakers tended viding a thermostatica-lly operated relay, it

is not only necessary that the current reach a certain value but that it persist for a suficiently long period to heat the thermostatic element to the bending point, thus rendering the relay unresponsive to even much greater currents which do not persist for a dangerous period. V

The thermostatic relay can also be madevery sensitive to long continued overloads of a much smaller value, these overloads being dangerous to the apparatus.

From theforegoing description it will be seen that my invention is very sensitive, this being becausev of the thermostatic means for breaking the throw-out switch'. This is an important feature of the invention. Another important, feature of the invention is that the thermostatic elements 4l may be easily and accurately adjusted so that the main circuit to the motor 86 (or to any other electrical machine) may be broken when any predetermined maximum current fiow is exceeded. Another feature is that there is a heating element 28 in each of the three phases of the circuit and when any one of these phases draws an excessive current the throw-out switch will be released. Another feature is the ease with which it may be re-set.

I claim as my invention:

A 1. An overload relay comprising: a throwout switch; an engager for retaining said throw-out switch closed; an adjustment member; a thermostatic elementcarried by said adjustment member, said thermostatic element being adapted to operate said engager to release said throw-out switch; adjustment means for adjusting the position of said adjustment member so that said thermostatic element may be made to operate said throw-out switch at the occurrence of a predetermined condition; and a heating element adapted to be connected in an electric circuit, for actuating said thermostatic element.

2. An overload relay comprising: a throwout switch; an engager for retaining said throw-out switch closed; an adjustment compression spring surrounding said shaft and forcing against said adjustment member; a nutscrewed onto said shaft, said nut being arranged to control the position of said shaft for adjusting the position of said adjustment member so that said thermostatic element may be made to operate said throw-out switch at the occurrence of a predetermined condition; and a heating element adapted to be connected'in an electric circuit, for actuating said thermostatic -element.

3. An overload relay comprising: a throwout switch; an engager for retaining said throw-out switch closed; an adjustment member, said adjust-ment member being pivoted; a thermostatic element carried by said adjustment member, said thermostatic element being adapted to operate said engager to release saidthrow-out switch; adjustment means for adjusting the position of said adjustment member so that said thermostatic element may be made to operate said throwout switch at the occurrence of a predetermined condition; and a heating element adapted to be connected in an electric circuit, for actuating said thermostatic ele'- ment. i

4. An overload relay comprising: a throwout switch; an engager for retaining said throw-out switch closed; an adjustment member, said adjustment member being pivoted; a thermostatic element carried by said adjustment member, said thermostatic element being adapted to operate said engager torelease said throw-out switch; a shaft engaging said adjustment member; a compression spring surrounding said shaft and forcing against said adjustment member; a

nut screwed onto said shaft, said nut being. arranged to control the position of said shaft for adjusting the position of said adjustment member so that said thermostatic element 4may be made to operate said throw-out switch at the occurrence of a predetermined condition; and a heating element adapted to be connected in an electric circuit, for actuatng said thermostatic element.

In testimony whereof, I have hereunto. set my hand at Los Angeles, California, this 21st day of December, 1926.

JOSEPH H. PEN GILLY. 

